In 30 years, William will be 3 times as old as he is right now. How old is he right now?
Explanation: We can use the given information to write down an equation about William's age. Let William's age be $w$ In 30 years, he will be $w + 30$ years old. At that time, he will also be $3 w$ years old. Writing this information as an equation, we get: $w + 30 = 3 w$ Solving for $w$ , we get: $2 w = 30$ $w = 15$.